Allocation of nitrogen to an inducible defense and seed production in Nicotiana attenuata.

Resource-based tradeoffs in the allocation of a limiting resource are commonly invoked to explain negative correlations between growth and defense in plants, but critical examinations of these tradeoffs are lacking. To rigorously quantify tradeoffs in a common currency, we grew Nicotiana attenuata plants in individual hydroponic chambers, induced nicotine production by treating roots with methyl jasmonate (MJ) and standardized leaf puncturing, and used N to determine whether nitrogen-based tradeoffs among nicotine production, growth, and seed production could be detected. Plants were treated with a range of MJ quantities (5, 45 or 250 μg plant) to effect a physiologically realistic range of changes in endogenous jasmonic acid levels and increases in nicotine production and accumulation; MJ treatments were applied to the roots to target JA-induced nicotine production, since nicotine biosynthesis is restricted to the roots.

Fire, nitrogen, and defensive plasticity in Nicotiana attenuata.

Nicotiana attenuata is a post-fire annual that utilizes jasmonate-inducible nicotine production as an inducible chemical defense which, in turn, can utilize 6% of a plant' s nitrogen budget and be costly to seed production. We characterize the nitrogen pools of burned soils in the plant' s native environment (piñyon-juniper woodlands) and examine how variation in nitrogen source and supply rate influence the patterns of allocation to growth and inducible and constitutive nicotine production. Available soil nitrogen increases dramatically (40-fold) immediately after a fire and consists principally of ammonia which is subsequently oxidized to nitrate during post-fire succession.

Within-plant relationships among wounding, jasmonic acid, and nicotine implications for defence in Nicotiana sylvestris.

In Nicotiana sylvestris Spegazzini and Comes (Solanaceae), we examined the relationships among wounding, endogenous leaf jasmonic acid (JA) pools, and whole-plain (WP) nicotine accumulation over a range of wounding intensities and spatial distributions, in order to explore optimal defence (OD) theory predictions. We quantitatively wounded one or four leaves and then quantified: (1) JA in damaged and undamaged leaves 90 min after wounding; (2) WP nicotine concentration after 5 d (the times when JA and nicotine attain the largest wound-induced concentrations). We find: (1) statistically significant, positive relationships on a leaf-by-leaf basis among the number of leaf punctures, endogenous leaf JA, and WP nicotine accumulation; (2) that young, undamaged leaves have a higher concentration of JA than do older, undamaged leaves, and produce a greater amount of JA per puncture than older leaves, but that all leaves have the same JA content (ng JA per leaf); and (3) that a damaged leaf produces less JA when other leaves in the canopy are wounded than when it is the onh wounded leaf in the canopy, but that when it is the only wounded leaf, the phylotactically adjacent, undamaged leaves do not increase their JA concentrations.